Sonoma Technology works with multiple oil refineries to perform fenceline monitoring of refinery emissions to address Federal regulations. Fenceline monitoring is intended to ensure that hazardous air pollutant emissions from refineries are controlled, with specific control actions required if fenceline concentrations exceed a specified level. Measurements include 14-day benzene passive samples collected every 2,000 feet around refinery fencelines. Our engineers and technicians performed pilot fenceline sampling at multiple refineries for up to a year to better understand benzene concentrations in advance of the official sampling. We continue to perform passive sampling to meet Federal regulations.